The present invention relates to an image forming apparatus which forms an image on a recording material by employing a recording element, and more particularly, to an image forming apparatus having therein a storage means that stores plural recording energy control data (hereinafter, referred to as recording energy control units), a discriminator means for discriminating the kinds of recording materials and means for switching a setting of the recording energy control units based on information discriminated by the discriminator means.
In an image recording apparatus wherein a silver halide photosensitive material is subjected to exposure and recording in accordance with image information, there is known a system employing a print head (array-type head) in which a plurality of recording elements (light sources) are arrayed in a line, as a method having various merits such as low cost, a compact apparatus, a easiness to obtain high quantity output, etc.
There has been proposed an apparatus wherein a vacuum fluorescent tube light source called VFPH (Vacuum Fluorescent Print Head) is used as the print head, stated above. The vacuum fluorescent tube light source has special features such as easily obtained high luminance, quick response and a slim body. By the way, a zinc oxide phosphor is selected as a phosphor mainly from the viewpoint of durability.
Further, an LED array light source is sometimes used in conjunction with the aforesaid print head, and with regard to a red color, in particular, a high density array such as 300 dpi or 400 dpi can be manufactured through a photomask method, whereby it is possible to create a structure employing an LED array as a red color light source and employing the VFPH mentioned above as a green color light source and a blue color light source, for example.
In recent years, there has been attempted development of an image recording apparatus wherein a silver halide color photosensitive material is subjected to digital exposure conducted by the array-type print head stated above, and then is subjected to automatic development.
In the image recording apparatus in which the digital exposure unit stated above is incorporated, continuous tone presentation is realized by changing luminous time of each recording element, as a method to record images through density modulation.
However, the luminous time can not be established individually for each recording element, and there is a restriction that the only available control is to allow all pixels to emit light for the same period of time or not to allow light emission at all. In addition, for the exposure, there is frequently conducted scanning exposure which, however, has a restriction that the time required to record one pixel is fixed because the scanning speed in such scanning exposure is determined to be constant in advance.
Under the restriction stated above, a bit separation multiple exposure system is used to speedily and efficiently control light emission in the digital exposure.
For example, a duration of 2.8 msec is divided into 12 luminous time (2.sup.n wherein n=0-11) including 2.sup.0, 2.sup.1, 2.sup.2, 2.sup.3, 2.sup.4, 2.sup.5, 2.sup.6, 2.sup.7, 2.sup.8, 2.sup.9, 2.sup.10 and 2.sup.11 in advance as shown in FIG. 15, and a combination of ON/OFF activations of the 12 luminous times is used.
Namely, to obtain a continuous tone, the unit of the 12 luminous times mentioned above are stipulated as 2.sup.n (separated in a binary system).
In the case of an LED, one bit corresponds to 100 nsec, while, in the case of VFPH, one bit corresponds to 300 nsec.
Therefore, when trying to emit light for the period of (1) 6400 nsec by the use of an LED, exposure of 64 bits representing 2.sup.6, namely, single exposure of n=6 is enough.
When trying to emit light for the period of (2) 6300 nsec, on the other hand, it is necessary to conduct exposure 6 times, which corresponds to n=0-5, because 63=32(=2.sup.5)+16(=2.sup.4)+8(=2.sup.3)+4(=2.sup.2)+2(=2.sup.1)+1(=2.sup. 0).
However, when exposing a photosensitive material by the use of the aforesaid unit of luminous times, there are caused the following problems;
(1) neither the rise nor the fall is zero in switching characteristics of light sources for light emission, and PA0 (2) energy for obtaining continuous tone can not be realized by a simple sum of time because photosensitive materials have high intensity reciprocity law failure characteristics and multiple exposure characteristics. PA0 (1) A recording element is a light emitting element, and various recording materials are silver halide photosensitive materials. PA0 (2) A discriminator means is a means to discriminate recording materials directly. When the aforesaid recording material is a roll-type photosensitive material, a discriminating action of the discriminator means is performed by detecting information which is provided on the tip of a photosensitive material to discriminate the photosensitive material, and also information in regard to whether the photosensitive material is a combination of one, two or more bar codes, punched holes, reflectance in light irradiation, and surface density or surface color. PA0 (3) A discriminator means is a means which discriminates information provided on a package means of a recording material. PA0 (4) A discriminator means is a means which discriminates information of the width of the recording material. PA0 (5) A discriminator means is an automatic discriminating means. PA0 (6) A recording element is a light emitting element, and a recording energy control unit is the emission control time of the recording element, or the recording energy control unit is only a combination of emission control time, or the emission control time is a.times.2.sup.n .+-..alpha. (nsec) (provided that a represents a coefficient for converting to time, and .alpha. is an adjustment factor), and further, the light emitting element is incorporated in an array-type head. PA0 (7) A recording element is a heat generating body, and recording energy control unit is heat generation control time.
With regard to the problem (2) above, in particular, it varies depending on the types and layer structures of the photosensitive materials, which can also be a problem. Accordingly, when images are outputted onto a photosensitive material of a different type with a fixed unit of luminous time, it is impossible to obtain a continuous tone, which is a problem.
The problems stated above are also caused on a heat generating body, in addition to the case wherein a recording element is a light emitting element, and a solution of the problems is delayed.